d=20150317&t=2&i=1033243739&w=580&fh=&fw=&ll=&pl=&r=LYNXMPEB2G131" alt="United States Ambassador to the United Nations Samantha Power addresses members of the U.N. Security Council during a meeting about Ukraine situation, at the U.N. headquarters in New York, March 6, 2015. REUTERS/Eduardo Munoz" style="display: block; max-width: 580px;" border="0">

United States Ambassador to the United Nations Samantha Power addresses members of the U.N. Security Council during a meeting about Ukraine situation, at the U.N. headquarters in New York, March 6, 2015.

CREDIT: REUTERS/EDUARDO MUNOZ

(Reuters) - A lack of accountability in South Sudan for "atrocities, sexual and gender based violence, child soldier recruitment and mass graves" hinders a bid for peace in the world's youngest state, the U.S. envoy to thehttp://www.reuters.com/subjects/united-nationsUnitedNationssaid on Tuesday.

Fighting since December 2013 between forces loyal to President Salva Kiir and rebels allied with his former deputy Riek Machar has reopened ethnic fault lines that pit Kiir's Dinka people against Machar's ethnic Nuer forces.

At least 10,000 people have been killed and 1.5 million civilians displaced.

U.S. Ambassador to theUnited Nations, Samantha Power, told reporters that until an accountability mechanism was in place then a "kind of collective ascription of responsibility is going to remain a major impediment to peace and to trust."

Power said: "This notion that accountability can wait because peace has to come first is just an inherently flawed and self-defeating notion." She said "this is a scale of atrocities and sexual and gender based violence and child soldier recruitment and mass graves that warrants, by any objective measure, accountability."

Talks between Kiir and Machar are being brokered by the eight-member East African bloc IGAD. The mediator, Ethiopia's Prime Minister Hailemariam Desalegn, berated both leaders on March 6 when the talks broke up.

There is widespread international frustration at the lack of progress in the peace talks.

Power and the U.N. Security Council discussed South Sudan, which declared independence from Sudan in 2011, with the African Union Peace and Security Council in Ethiopia last week.

The African Union in January shelved a Commission of Inquiry report into the conflict and how South Sudan could move forward because of fears publication could disrupt peace negotiations, AU diplomats said.

A draft of the report, produced in October and seen by Reuters, calls for Kiir and Machar to be barred from any transitional government in South Sudan. It said the violence "ethnically cleansed" the capital Juba of Nuer, which then led to revenge attacks elsewhere.

The recommendation is at odds with a potential peace deal that would retain Kiir as president and appoint Machar deputy.

The U.N. Security Council has urged the African Union to publicly release the findings. TheUnited Nationsand aid agencies have accused both sides of human rights violations.